During a hike of the countryside, the Hardy boys and their pals learn that an abandoned mill has recently gotten new owners. When the boys go to look, the new owners claim to be producing a new breakfast food, field a few questions, and then shoo the boys away. But that’s enough to make the Hardy boys suspicious. Are the men to be trusted? Are they merely surly scientists, or are they covering up a darker secret?

This is the third book of the Hardy boys series, first published in 1927. It was rewritten in 1962; this Standard Ebook contains the original 1927 text.